Process for the production of elastic crimped filaments



United States Patent Int. or. plu 1/02 US. Cl. 57157 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a process for the production of elastic voluminous crimped filaments from synthetic polymers especially from synthetic linear high molecular weight polyamides which comprises a two-step treatment of the filaments. In the first step the unstretched filaments were subjected to a false-twist crimping and stretching under heating and subsequently cooling the filaments. The stretching being effected without the aid of a Stretching pin. In the second step the filaments being subjected to a further false-twist crimping in the opposite direction, and a further stretching and cooling operation. The filaments being relieved of tension or subjected to a shrinking procedure.

This invention relates to a process for the production of moderately elastic highly voluminous crimped filaments in which filaments of synthetic high polymers are subjected to false-twist crimping under the influence of heat, accompanied by stretching.

It is known that crimped filaments can be produced from synthetic high polymers by false twisting under the influence of heat during the stretching process, followed by a bulking process. In order to establish a fixing point, a stretching pin is located in front of the heating element in the stretching zone. In this process, fixing does not in itself have to satisfy the final requirements because a subsequent washing cycle is used to develop the crimp and to fix it under an appropriate increase in temperature.

In this known process in which the filament is stretched in the crimping zone by means of a stretching pin arranged in front of the heating zone in the path followed by the filament, the filament is under considerable tension during fixing so that, under full stretch, the crimp is not stable enough for subsequent application. The loops are small and irregular. For this reason, the material cannot be fully stretched by this process.

A process for the continuous production of moderately elastic, highly voluminous crimped filaments from synthetic high polymers, has now been found which does not have the disadvantages affecting the conventional process. In the process according to the invention, unstretched filaments of synthetic high polymers, synthetic linear high molecular weight polyamides in particular, are subjected in a first stage to false twist crimping under heat, accompanied by stretching, and in a second stage to another false twist crimping operation in the opposite direction, accompanied by further stretching, and are then relieved of tension or shrunk. The first stage of the process is preferably carried out at a temperature from 160 to 180 C. and the second stage at a temperature from 130 to 150 C. In the first stage, stretching is from 200 to 250% and in the second stage from to 50%. Shrinkage or contraction amounts to from to 35%.

In the process according to the invention, the filament taken from the bobbin is continuously stretched and at the same time additionally false-twisted and heat-treated and 3,503,201 Patented Mar. 31, 1970 See then false-twisted in the opposite direction under tension and stretch. Finally, it is relieved of tension and so contracts. As a result, the crimped filament has no tendency to rotate and does not have to be twisted with another crimped filament tending to rotate in the opposite direction. The yarn thus obtained is moderately elastic, smooth and has little or no residual shrinkage.

In the process according to the invention, the filament is stretched in two parts, accompanied by twisting. The actual process of stretching takes place in the absence of any definite stretching point between the delivery rollers and the false twist spindle for the first part of the crimp in particular, so that the stretching zone in adjusted in dependence upon the cooling zone due to the temperature set in the heating element. The filament thus crimped and stretched twice is then subjected to a tension-relieving or shrinkage process. In the first stage, the twist applied to the travelling filament is from a half to once the normal twist and, in the second stage, is from once to one and a half times the normal twist (according to Heberleins twist formula as reported in Melliand Textil-berichte 3, 1966, page 239).

To carry out the process, the filament is stretched between the three delivery mechanisms in the heating unit in the absence of any definite stretching point. The twister does not perform the function of a stretching point, but merely transmits the torque to the cooled, stretched filament. For this reason, the filament is subjected to slight tension during fixing so that the crimp is formed normally. Residual shrinkage is reduced. A somewhat higher stretching ratio may also be used. Subsequent crimping in the opposite direction under tension ensures that the yarn is produced satisfactorily without rotation under the final degree of stretching, whilst the subsequent tension-relieving or shrinkage treatment makes it possible to produce filaments that can be satisfactorily processed.

It is possible by means of the process according to the invention to produce crimped yarn from the bobbin so that the need for otherwise usual operations is dispensed with. The crimped yarn has an appearance of the kind that can only be obtained in several operations with conventional machines (draw-twisting machines and special false-twisting machines incorporating an after-treatment unit The following example shows more particularly the process according to the invention.

EXAMPLE A filament of poly-e-caprolactam den.) is stretched in a ratio of 1:3.12 at C. in a heating tube (first stage) and at the same time is twisted in the S-direction by means of a twist spindle rotating at 1860 r.p.m. The filament, thus stretched and crimped, is twisted in the Z-direction in a second heating zone at 135 C. (2200 r.p.m.) and at the same time is stretched by 15%. The filament, thus stretched and false-twist crimped in two stages, is wound up under 15% shrinkage. This material is used for a knit fabric which is piece-dyed and finished. The filament thus crimped has a contraction through crimping (Melliand Textilberichte 5, 1966, page 439) of 25 to 30% and a residual shrinkage of about 8%. The filament does not have any tendency to stretch and may be processed as a monofilament. It is particularly suitable for use in monofilament processing, as a weft yarn in weaving and for weave-knit fabrics in the knitting field. In cases where it is used for articles produced with dyed yarns, the filament is not only relieved of tension, but is also continuously subjected to a shrinkage process at C., the residual shrinkage amounting to 2.5%. In this case, subsequent winding to relieve the yarn of tension takes below 35%.- The packages thus produced can be directly dyed by the creel process.

What we claim is:

1. A process for continuous production of moderately elastic highly voluminous crimped filaments from synthetic polymers, by false-twist crimping, which comprises subjecting the unstretched filaments, in a first step, to a false-twist crimping under heat, and simultaneously stretching the filaments without the aid of a stretching pin and cooling, and, in a second step, subjecting the filaments to a further false-twist crimping operation under heat in the opposite direction and a further stretching without the aid of a stretching pin, cooling the filaments again and relieving the tension.

2. The process of claim 1, wherein the false twisting of the first stage is carried out with the same or slightly less rotation than the false-twist crimping of the second stage.

3. The process of claim 1, wherein the stretching operation in the first stage is carried out at a temperature from 160 to 180 C. and in the second stage at a temperature from 130 to 150 C.

References Cited UNITED STATES PATENTS 12/1947 Truitt 57l57 XR 7/1962 Held 5734 6/1964 Crouzet 57157 5/ 1967 Gilchrist 5734 FOREIGN PATENTS 7/1955 Australia 7/ 1959 Australia. 12/ 195 9 Australia.

2/ 1964 Australia.

U.S. Cl. X.R. 

